The invention relates to a combined solar and wind energy converstion system which is capable of producing an output of electricity continuously even during times when the solar and wind energy available are insufficient to produce the quantity desired.
Various prior art techniques have been disclosed for generating electricity both as a result of solar energy and as a result of wind movement. However, the advantages attendant upon combining both types of energy generation into a single system which is capable of operating over long periods of time at a very high efficiency even when sufficient quantities of solar and wind energy are unavailable over relatively long periods of time are generally unknown.
In one prior art process such as that disclosed in U.S. Pat. No. 3,903,700 water is raised from a lower tank to an upper tank by means of solar energy. As water is drained from the upper tank back into the lower tank, it operates a hydro-electric generator. However, this system is generally quite inefficient in energy conversion as steam pressure generated in the solar collector is used to drive a turbine which pumps the water from the lower level to the higher level. With pressures typically attainable with solar collectors and the conversion efficiencies of typical turbine pumps, the system efficiency was generally believed to be quite low.
Other techniques, such as that disclosed in U.S. Pat. No. 2,688,923, have utilized solar energy for raising a working fluid such as water from a lower level to a higher level. In this system, containers are filled with water through a valve at the bottom. After the valve is closed, pressure generated by the steam in the solar collector forces the water in the containers up to a higher level. This system is believed to be generally costly and unwieldly as well as being inefficient in that each container requires its own steam generator within the solar collector. Also, there is no utilization of the water at the higher level for generating electricity.
Other complex and generally inefficient systems have been proposed for utilizing solar energy to raise a liquid from a lower level to a higher level for generation of electricity. In U.S. Pat. No. 3,937,599 there is disclosed a system which uses a pump operating with a vaporizable fluid flowing in a closed circuit between a solar evaporator and a condenser. Two separate fluids are required in this system, one to drive the pump and the other to generate the electricity.
Many other types of solar energy converters have been disclosed, for example, those of U.S. Pat. No. 4,031,703; U.S. Pat. Nos. 4,055,948 and 4,089,174. These are merely examples of the myriad of different solar energy conversion systems which have heretobefore been proposed but which are not capable of producing electrical energy continuously over relatively long time periods and which are adaptable for combination with a wind energy conversion system.